title: Intra- and intermolecular regulatory interactions in Upf1, the RNA helicase central to nonsense-mediated mRNA decay in yeast.
abstract: RNA helicases are involved in almost every aspect of RNA metabolism, yet very little is known about the regulation of this class of enzymes. In Saccharomyces cerevisiae, the stability and translational fidelity of nonsense-containing mRNAs are controlled by the group I RNA helicase Upf1 and the proteins it interacts with, Upf2 and Upf3. Combining the yeast two-hybrid system with genetic analysis, we show here that the cysteine- and histidine-rich (CH) domain and the RNA helicase domain of yeast Upf1 can engage in two new types of molecular interactions: an intramolecular interaction between these two domains and self-association of each of these domains. Multiple observations indicate that these molecular interactions are crucial for Upf1 regulation. First, coexpression of the CH domain and the RNA helicase domain in trans can reconstitute Upf1 function in both promoting nonsense-mediated mRNA decay (NMD) and preventing nonsense suppression. Second, mutations that disrupt Upf1 intramolecular interaction cause loss of Upf1 function. These mutations weaken Upf2 interaction and, surprisingly, promote Upf1 self-association. Third, the genetic defects resulting from deficiency in Upf1 intramolecular interaction or RNA binding are suppressed by expression of Upf2. Collectively, these data reveal a set of sequential molecular interactions and their roles in regulating Upf1 function during activation of NMD and suggest that cis intramolecular interaction and trans self-association may be general mechanisms for regulation of RNA helicase functions.
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.forename: Robin
authors.initials: R
authors.lastname: Ganesan
authors.forename: Allan
authors.initials: A
authors.lastname: Jacobson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D016297:Mutagenesis, Site-Directed; D010443:Peptide Chain Termination, Translational; D054730:Protein Interaction Domains and Motifs; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020798:Two-Hybrid System Techniques
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C092470:NMD2 protein, S cerevisiae; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases